1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a LCD device that substantially prevents a semiconductor layer from being excited.
2. Discussion of the Related Art
Generally, a LCD device displays images by controlling a light transmittance of liquid crystal with an electric field. For this, the LCD device includes a LCD panel which includes liquid crystal cells arranged in a matrix configuration, a driving circuit which drives the LCD panel, and a backlight unit which emits a light to the LCD panel.
The LCD panel also includes a thin film transistor array substrate, a color filter array substrate, a spacer, and a liquid crystal layer. The thin film transistor array substrate may be positioned opposite the color filter array substrate. The spacer maintains a predetermined cell gap between the two substrates. The liquid crystal layer is formed in the cell gap provided between the two substrates.
The thin film transistor array substrate includes multiple gate lines, multiple data lines, a thin film transistor, a pixel electrode, and an alignment layer. Each gate line is formed perpendicular to each data line to define a unit pixel. The thin film transistor is
formed adjacent to a crossing portion of the gate and data lines. The pixel electrode is formed near each liquid crystal cell and is connected to the thin film transistor. The alignment layer is applied over the pixel electrode and the thin film transistor. The gate and data lines receive signals from driving circuits. The thin film transistor supplies a pixel voltage signal transmitted through a data line to the pixel electrode in response to a scan signal transmitted through a gate line.
The color filter array substrate includes multiple color filters, a black matrix, and a common electrode. The multiple color filters are provided to the respective liquid crystal cells. The black matrix divides the color filters, and may substantially prevent light from leaking between the filters. The common electrode may supply a reference voltage to the liquid crystal cells. An alignment layer may be applied to the color filter array substrate.
After separately forming the thin film transistor array substrate and the color filter array substrate, the two substrates may be bonded to each other. Liquid crystal may then be injected into the cell gap between the two substrates.
The thin film transistor array substrate of the LCD panel is fabricated by multiple mask and semiconductor steps. The fabrication of the LCD panel can be a complicated and complex process and may include high fabrication costs. Each mask step can include deposition of a material, cleaning, photolithography, etching, photoresist stripping, and inspection. To form the thin film transistor array substrate, five masks are generally used. Reduction of the number of masks used can reduce the complexity and cost of the fabrication process. The fabrications of some LCD devices use four masks to form the thin film transistor array substrate. In these fabrications, one mask step can be eliminated by forming a semiconductor layer and a data line are formed at the same time.
FIG. 1A is a diagram of a backlight driving signal driven in a continuous mode. FIG. 1B is a diagram of a backlight driving signal driven in a burst mode. As shown in FIG. 1A, the backlight unit is continuously maintained in the turned-on state. Driving the backlight unit in this manner can increase power consumption of the LCD device. In order to decrease the power consumption, the backlight unit may be driven in the burst mode.
For the burst mode, as shown in FIG. 1B, the backlight unit is turned-on for a portion of time and turned-off for a portion of time. This turned-on and turned-off cycle may be repeated for a preset period of time. When the backlight unit is turned-on in the burst mode, a photocurrent can excite a semiconductor layer in a portion of a LCD panel's data line making the semiconductor layer act as a conductor. During the time period when the backlight unit is turned-off, this semiconductor layer is no longer excited and does not act as a conductor.
When the semiconductor layer becomes conductive, a capacitance occurs between the semiconductor layer and the pixel electrode. However, when the semiconductor layer is the nonconductive, a capacitance occurs between the data line and the pixel electrode. Depending upon the state of the backlight unit driven in the burst mode, different capacitances may be generated. The different capacitances generated between the semiconductor layer and the pixel electrode or between the data line and the pixel electrode can cause noise in the LCD device. This noise can adversely affect the picture quality of the LCD device. Therefore, a need exists for an improved LCD device.